Define the independent and dependent variables, specify apparatus range or resolution, control conditions and explain how preliminary trials set timings or concentrations.
The photograph shows a sea slug of the genus Aplysia, a marine animal.
external gills; © walkdragon/Shutterstock
Magnification ×1.0
Aplysia can be kept in tanks in a laboratory.
Aplysia absorb oxygen using external gills.
When the gills are touched, the gills are completely withdrawn into the body by a reflex action.
The gills re-emerge after some time.
The student formed the following hypothesis:
The more frequently the gills are touched the less time it takes them to re-emerge.
Plan an investigation to find evidence to support or reject this hypothesis.
Devise a detailed method, including an explanation of how you would control and monitor important variables.